1. Field of the Invention
This invention relates to locking devices for mechanical control mechanisms or switches.
2. Description of the Prior Art
Control mechanisms comprising a lever arm projecting from a rotatable base having projecting stop portions are wellknown and commonly used in a variety of control applications. The lever arm or operating element is capable of movement in either direction about the axis of its rotatable base with the degree of movement limited by the stop portions which project from each side of the base. The rotatable base is mounted on the end of the shaft to which the control means are connected within a housing. The shaft is turned or oscillated by manual operation of the lever arm.
When projecting vertically upright, the lever arm is usually in its inoperative or neutral position with the base midway between its limiting stop positions, so that the control means connected to the shaft are inoperative. The lever arm is capable of moving to either of two operative positions at each of which one of the stop portions of the base contacts a fixed stop mounted adjacent to the base.
It is often desirable to maintain a lever arm in its neutral upright position for extended periods of time. However, in this position the lever arm is extremely susceptible to being bumped or hit, which may cause inadvertent movement of the lever arm which movement would be undesirable and may even be disastrous depending upon the mechanism being controlled.
Various devices have been developed for locking switches, handles and other elements to prevent inadvertent movement thereof. For example, U.S. Pat. No. 3,980,099, issued to G. V. Youngblood, discloses a guard which attached over the rotatable handle of a valve. U.S. Pat. No. 3,522,746, issued to C. C. Reynolds, discloses a safety device for mounting over the projecting lever of a control element. U.S. Pat. No. 3,595,040, issued to R. D. Curl, discloses a locking attachment securable to the porjecting switch lever of a circuit breaker. All of these devices require some form of attachment over or around the projecting lever arm of the control device. In many instances, such attachment would be bulky, difficult to attach, and complicated in structure. In addition, the device mounted over the lever arm could obstruct other apparatus in proximity to the lever arm and thus cause more problems than it solves.